I noticed that there are several QRP transceivers that use 4.9152 MHz intermediate frequency. For instance, John Dillon, WA3RNC uses it in Penntek TR-25, TR-35 and TR-45 transceivers. Also a very close frequency (4.914 MHz) is used in Elecraft KX1.
Does anyone know what is so special about this particular frequency? Does this has something to do with avoiding spurious signals? Or this frequency just happened to be convenient in terms of availability / price of the crystals, filter impedance / bandwidth, the fact that it's easier to get more gain on lower frequencies (comparing to 9 Mhz or 12 Mhz), etc? Or maybe there is some other reason?